Unlike semiconductor processing on silicon-based wafers, which has been studied and refined for more than half a century, gallium nitride processing is a relatively new technology, for which standardized testing is still being devised. In particular, in GaN high voltage technology, no standard qualification criteria have yet been determined. Processes are needed that can validate GaN and similar devices for long term use in a relatively short amount of time.
Due to the high critical electric field of GaN, Time Dependent Dielectric Breakdown (TDDB) can be one of the main factors that limit the device lifetime. Most GaN high voltage devices utilize a structure that includes multiple field plates to shield underlying structures from the high voltages present. However, the presence of multiple field plates increases the challenge in determining the TDDB lifetime of the inner field plate region due to the electric field shielding from the outer field plates.